Wafers of a semiconductive material such as a single crystal of Si or Ga--As compounds are produced by slicing a rod of the material using a saw blade. The saw blade normally comprises a substrate in the shape of a very thin disc onto which diamond is electrically deposited. More particularly a thin annular disc having a round hollow scooped at its center is used as the substrate, and along the peripheral edge portions of the round hollow particulate diamond is electrically deposited with a width of several millimeters to provide a blade edge. Upon slicing a rod of a semiconductive material to wafers, the saw blade is rotatably mounted on a slicing machine, and the rod is passed through the round hollow of the rotating blade so that the edge portions of the round hollow may serve as the slicing blade edge.
As a substrste of such saw blade use has heretofore been made of stainless steels, such as thin cold rolled materials of SUS304 and SUS301, optionally age hardened. A thin substrate of such a material poses a problem in that it frequently undergoes, because of its low strength, shape distortion and/or fatigue breakage during service, rendering the service life of the saw blade short, and therefore, it has been necessary to use a relatively thick substrate. However, the thicker the substrate the more the slicing loss. It is important to achieve the smallest possible slicing loss to prevent reduction of the yield.
As an approach it has been proposed to use as the substrate of a saw blade a drastically cold worked material of a quasi-stable austenitic stainless steel, such as SUS301, which material exhibits a satisfactory strength even with a thin thickness. In this case, however, the drastic cold working results in reduction of toughness and elongation of the material. Accordingly, the substrate made of such a material may break at the time the saw blade is mounted on a slicing machine, or may tear during service to destroy the material being sliced, such as a single crystal of Si.
As another approach there has been an attempt to use as the substrate of a saw blade a certain precipitation hardenable stainless steel, such as SUS631. This steel can be age hardened to a certain level of strength. However, it contains Al, which is an element having great affinity to oxygen and nitrogen, in an amount of from 0.75 to 1.5%, posing problems, including formation of aluminous non-metallic inclusions during steel making, formation of A1N and aggregated inclusions thereof during casting, not only rendering surface textures of the product coarse, but also adversely affecting toughness and elongation, leading to a remarkably shortened fatigue life of the product. The above-mentioned precipitation hardenable steel is not completely satisfactory as a material for the substrate of slicing saw blades.